U.S. trade regulators are examining links between Apple Inc. and Google Inc. as the two tech giants share some board members.

Both Arthur Levinson, former CEO of Genentech Inc. and Google’s CEO, Eric Schmidt, sit on the boards at Apple and at Google. Under the Clayton Antitrust Act of 1914, directors are forbidden from sitting on the board of two companies where that would reduce competition. It's a rarely enforced ruling, and where it does become an issue the norm is for the director concerned to resign from one of the boards.

The New York Times and Wall Street Journal both reported that the Federal Trade Commission is looking at the two businesses, which compete in several markets, particularly in mobile phones.

Apple makes the popular iPhone, which comes loaded with several Google apps like its map service, while Google makes its own Android phone software.

Google directors also have plenty of board positions in other tech companies; one Google director is Intel CEO Paul Otellini, and another is L John Doerr, who is also on the board of Amazon.

Other Apple board members include former U.S. Vice President Albert Gore, J. Crew Group CEO Millard Drexler, Intuit Inc. Chairman Bill Campbell and Apple’s CEO, Steve Jobs.